Keratin is an animal protein which is nutritionally valuable, but not widely used and a fibrous component of skin, horns and hair and has been wasted in bulk in the slaughter and cattle industry (Kornillowicz-Kowalska and Bohacz, 2011).
Since the keratin contains many disulfide bonds in its structure, the keratin has a water-insoluble characteristic and is not decomposed by general proteases (Onifade et al., 1998).
Currently, keratin wastes are incinerated or after the keratin is decomposed by chemical methods, the degradation product thereof is recycled as feed additives for livestock. The keratin decomposition product generated by chemical treatment has a high content of nitrogen, fat, and the like, but has disadvantages in that the content of amino acids such as lysine and methionine which are required for livestock is low and simultaneously, digestibility is low (Papadoulos and Ketelaars, 1986). Further, high energy cost is required and environmental problems such as odor can occur (da Rosa Gioppo and the like 2009). Therefore, in order to solve the problems, a new treatment method has been required and recently, a keratin decomposition method by microorganisms has been actively studied as an eco-friendly alternative to solve the above problems.
A microbiological keratin treatment method started with the isolation of microorganisms producing keratin degrading enzymes, and various microorganisms such as Bacillus spp., actinomycetes and fungi were isolated from a natural environment and enzyme production characteristics and the nutritional value of keratin decomposition products treated with these microorganisms have been reported (Bertsch and Coello, 2005; Brandelli, et al., 2010). In addition, it was reported that the keratinase can be used for removal of proteinaceous organic materials in a wastewater treatment plant, improvement of fabric quality, hair removal of leather, exfoliating cosmetics, prion decomposition, and the like (Gupta and Ramnani, 2006; Langeveld, et al., 2003; Onifade, et al., 1998). Further, in order to pioneer novel applications, studies for isolating strains having unique properties such as plant growth promoting activity and antifungal activity, together with keratinase activity have been started (Jeong, et al, 2010).
Meanwhile, it is known that coenzyme is more advantageous than using a purified enzyme to decompose proteins at low cost and the coenzyme is more stable than the purified enzyme. Actually, the product in the coenzyme state is commercialized as an enzyme preparation for treating a large amount of proteins. Further, since the characteristics of the keratinase are strain-specific, physicochemical properties of the enzymes produced by each strain need to be investigated for efficient application of the enzyme.